So I will toss my limited knowledge into the ring and remind you that my advice is exactly worth what you pay for it! I did a lot of digging into both the HSS and Gibson Music Yo era of Slingerland snares when I did my Nashville Tribute snare and I learned a few things to look for.
Both companies used the same badge (HSS was early 90's while the Music Yo models were 10 years later in the early 2000's) so the serial number can help move the needle on that for sure. I agree with Peterk, I do not recall the later Gibson owned Music Yo drums having mufflers on the natural finished snares. Do you have the drum it's self? The shell can help narrow it down as well in the ply lay up and how the snare beds were cut. But without more, clear pics, I am standing on this being an earlier 90's HSS model.
I have a guy coming up that wants to trade some snares for an 30"WFL bass drum and this is one of the snares. I was asking $200 for the drum and I think he's bringing this and a Black Acro.I think your value is on target but they seem to sell for more. I remember some comments about the beds being very shallow but I could be wrong....and that's an easy fix.